SOMATIC AND GERMLINE CHICKEN CHIMERAS OBTAINED FROM BROWN AND WHITE LEGHORNS BY TRANSFER OF EARLY BLASTODERMAL CELLS

Stage X blastodermal cells were isolated from freshly laid unincubated Brown Leghorn chicken eggs. Five hundred cells from Stage X Brown Leg horn embryos were injected into the subgerminal cavity of White Leghor n unincubated embryos exposed to 550 rad of gamma irradiation from a c esium-137 source. Of 712 White Leghorn embryos that were irradiated an d injected with Brown Leghorn blastodermal cells, 52(7.3%) survived to hatching. Somatic chimerism was examined in the melanocyte population and erythroid lineage. The presence of brown feathers indicating dono r cell contribution to melanocyte pigmentation was observed in 23(44%) out of the 52 hatched chicks. Analysis of blood DNA was performed usi ng a probe that revealed an endogenous retroviral gag fragment specifi c for the donor genome. Three out of these 23 chimeric chickens exhibi ted the gag-specific fragment. To test germline chimerism, chickens th at reached sexual maturity were mated with Brown Leghorns. Three somat ically chimeric hens produced Brown Leghorn progeny at a rate of 30.7, 9.2, and 2.9% respectively, thus proving donor cell contribution to t he germline differentiation. Chimeric chickens obtained after injectio n of nonirradiated embryos exhibited a lower extent of chimerism at th e feather level and did not show any chimerism in the erythroid lineag e and the germline, thus demonstrating the value of the use of comprom ised recipient embryos to produce chimeras in chickens. Nevertheless, the extent of somatic chimerism could not be used to predict the germl ine chimerism.